WAFER LEVEL TRANSFER MOLDING AND APPARATUS FOR PERFORMING THE SAME
A method includes placing a package structure into a mold chase, with top surfaces of device dies in the package structure contacting a release film in the mold chase. A molding compound is injected into an inner space of the mold chase through an injection port, with the injection port on a side of the mold chase. During the injection of the molding compound, a venting step is performed through a first venting port and a second venting port of the mold chase. The first venting port has a first flow rate, and the second port has a second flow rate different from the first flow rate.
This application is a continuation-in-part application of the following commonly-assigned U.S. patent application: patent application Ser. No. 13/411,293, filed Mar. 2, 2012, and entitled “Wafer-Level Underfill and Over-Molding;” which application is hereby incorporated herein by reference.
BACKGROUNDIn the packaging of integrated circuits, package components, such as device dies and package substrates, are typically stacked through flip chip bonding. To protect the stacked package components, a molding compound is disposed surrounding the device die.
The conventional molding methods include compression molding and transfer molding. Compression molding may be used for over-molding. Since the compression molding cannot be used to fill the gaps between the stacked dies, the underfill needs to be dispensed in separate steps from the compression molding. On the other hand, transfer molding may be used to fill a molding underfill into the gap between, and over, the stacked package components. Accordingly, transfer molding may be used to dispense the underfill and the molding compound in the same step. Transfer molding, however, cannot be used on the packages including round wafers due to non-uniform dispensing of the molding compound.
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact and may also include embodiments in which additional features may be formed between the first and second features such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Further, spatially relative terms such as “underlying,” “below,” “lower,” “overlying,” “upper,” and the like may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
An apparatus for wafer-level transfer molding process and the method of performing the wafer-level transfer molding are provided in accordance with various exemplary embodiments of the present disclosure. The variations of the embodiments are discussed. Throughout the various views and illustrative embodiments, like reference numbers are used to designate like elements.
Mold chase 26 includes top portion (a cover) 26A, which may have a round top-view shape (
Mold chase 26 further includes edge ring 26B (also refer to
In some embodiments, as shown in
Through venting ports 32, the inner space inside mold chase 26 may be vacuumed. For example, pipes 52 (
As shown in
It is appreciated that the sizes of venting ports 32 may be directly related to the flow rate of gases through venting ports 32 since they share the same pressure of environment 36 and the same pressure of the inner space of mold chase 26. Hence, venting ports 32-1 through 32-m may have increasingly smaller flow rates of gas with the increase in the sequence number of the respective venting ports 32. Furthermore, venting port 32-1 may have the highest flow rate, and venting port 32-m may have the lowest flow rate.
In the embodiments in
In accordance with some embodiments, a molding process includes pumping gas/air out of environment 36, for example, through pump 44, since mold chase 26 is placed in environment 36, and venting ports 32 connect the inner space of mold chase 26 to environment 36. Hence, when molding compound 46 (represented by arrows) is injected into the inner space of mold chase 26, the vacuum in the inner space causes molding compound 46 to be pulled forward and fill the gaps between dies 22 and the gaps between dies 22 and wafer 20. In these embodiments, no pump and valve is connected to venting ports 32 directly.
As also shown in
In accordance with the embodiments of the present disclosure, venting ports 32 are connected to chamber 50 through the respective valves 48 and pipes 52, with some of pipes 52 represented using lines. Chamber 50 is vacuumed, for example, through pump 44. Accordingly, chamber 50 has a low pressure, for example, lower than about 10 torr. Valves 48 are opened differently in order to have different opening sizes so that the gas flow passing through different valves 48 are different. In accordance with some embodiments, with the increase in the sequence number, the openings (or apertures or the diameters of the openings) of the respective valves 48-1 through 48-m are increasingly smaller. Alternatively stated, with the increase in the sequence number, the flow rates of the respective valves 48-1 through 48-m are increasingly smaller.
As a result of the different flow rates of valves 48-1 through 48-m, molding compound 46 is pulled faster in the direction toward venting port 32-1 than other venting ports. Furthermore, from venting port 32-1 to venting port 32-m, the flowing speed of molding compound 46 is increasingly smaller to compensate for the increasingly smaller distances from the respective venting ports 32 to molding injection port 30. As a result, molding compound 46 may be filled into different portions of the inner space of mold chase 26 at the same time.
Referring to
Referring to
Next, as shown in
In subsequent steps, valves 48-4 through 48-m are opened sequentially, with each of valves 48 being opened after the opening time of the valves that have smaller sequence numbers. For example, referring to
The lagging of each of time points T2 through Tm relative to its preceding time points is controlled by controller 54, wherein the optimum time points Ti through Tm may be found through experiments and may be used for the same types of products as long as the design of the molded package structure and the type of molding compound remains unchanged.
As shown in
After the molding injection step occurs as shown in
In
The embodiments of the present disclosure have some advantageous features. In the embodiments of the present disclosure, a transfer molding method is used, with a release film contacting the top surface of the dies of the package structure that is molded. In the resulting molded package, the top surfaces of the device dies are exposed without the need of performing a grinding process to expose the top surfaces of device dies 22. In addition, the molding compound fills the gaps between dies 22 and wafer 20, and hence no additional underfilling step is needed. The molding compound fills the molding chase uniformly, and the efficiency of the molding process is improved.
In accordance with some embodiments of the present disclosure, a method includes placing a package structure into a mold chase, with top surfaces of device dies in the package structure contacting a release film in the mold chase. A molding compound is injected into an inner space of the mold chase through an injection port, with the injection port on a side of the mold chase. During the injection of the molding compound, a venting step is performed through a first venting port and a second venting port of the mold chase. The first venting port has a first flow rate, and the second port has a second flow rate different from the first flow rate.
In accordance with alternative embodiments of the present disclosure, a method includes placing a package structure into an inner space of a mold chase, with top surfaces of device dies in the package structure contacting a release film in the mold chase. The mold chase includes an injection port, and a first venting port and a second venting port that have different sizes. The method further includes placing the package structure and the mold chase in a chamber, wherein each of the first venting port and the second venting port interconnects the inner space to a portion of the chamber outside of the mold chase. The chamber is vacuumed. A molding compound is injected into the inner space of the mold chase through the injection port.
In accordance with yet alternative embodiments of the present disclosure, a mold chase includes a top portion, and an edge ring having a ring-shape, wherein the edge ring is underlying and connected to edges of the top portion. The edge ring encircles an inner space under the top portion. An injection port is connected to the inner space of the mold chase. A first venting port and a second venting port are at the edge ring, wherein the first venting port has a first size and the second venting port has a second size different from the first size.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.
Claims
1. A method comprising:
- placing a package structure into a mold chase, with top surfaces of device dies in the package structure contacting a release film in the mold chase;
- injecting a molding compound into an inner space of the mold chase through an injection port, with the injection port on a first side of the mold chase; and
- during the injecting the molding compound, venting through a first venting port and a second venting port of the mold chase, with the first venting port having a first flow rate and the second port having a second flow rate different from the first flow rate.
2. The method of claim 1, wherein the first venting port is farther away from the injection port than the second venting port, and wherein the first flow rate is higher than the second flow rate.
3. The method of claim 1, wherein the first venting port and the second venting port are both connected to a same vacuum environment, and wherein a first size of the first venting port is different from a second size of the second venting port.
4. The method of claim 1 further comprising a plurality of venting ports on the mold chase, wherein the plurality of venting ports is increasingly smaller with a reduction of respective distances from the plurality of venting ports to the injection port.
5. The method of claim 1, wherein the venting through the first venting port is controlled by a first valve, and the venting through the second venting port is controlled by a second valve, and wherein the first valve and the second valve control the first flow rate and the second flow rate, respectively.
6. The method of claim 5, wherein the first venting port is farther away from the injection port than the second venting port, and wherein the first valve and the second valve control the first flow rate to be greater than the second flow rate.
7. The method of claim 5, wherein the first valve and the second valve connect the first venting port and the second venting port, respectively, to a same vacuum chamber.
8. A method comprising:
- placing a package structure into an inner space of a mold chase, with top surfaces of device dies in the package structure contacting a release film in the mold chase, wherein the mold chase comprises: an injection port; and a first venting port and a second venting port having different sizes;
- placing the package structure and the mold chase in a chamber, wherein each of the first venting port and the second venting port interconnects the inner space to a portion of the chamber outside of the mold chase;
- vacuuming the chamber; and
- injecting a molding compound into the inner space of the mold chase through the injection port.
9. The method of claim 8 further comprising placing a release film in the inner space of the mold chase, with top surfaces of devices dies of the package structure contacting the release film.
10. The method of claim 8, wherein a first size of the first venting port is greater than a second size of the second venting port, and the first venting port is farther away from the injection port than the second venting port.
11. The method of claim 8, wherein the mold chase has a circular shape, with the first venting port and the injection port being on opposite sides of a diameter of the mold chase, and wherein the first venting port has a greatest size among all venting ports of the mold chase.
12. The method of claim 8 further comprising;
- curing the molding compound after the injecting the molding compound; and
- removing a package comprising the package structure and the molding compound from the mold chase.
13. The method of claim 8, wherein the package structure comprises:
- a wafer; and
- a plurality of dies over and bonded to the wafer, wherein in the injecting the molding compound, the molding compound flows from one side of the wafer to an opposite side of the wafer.
14. The method of claim 8, wherein no pump and no valve is connected to the first venting port and the second venting port.
15. An apparatus comprising:
- a mold chase comprising: a top portion; and an edge ring having a ring-shape, wherein the edge ring is underlying and connected to edges of the top portion, and wherein the edge ring encircles an inner space under the top portion;
- an injection port connected to the inner space of the mold chase; and
- a first venting port and a second venting port at the edge ring, wherein the first venting port has a first size and the second venting port has a second size different from the first size.
16. The apparatus of claim 15 further comprising a dispenser connected to the injection port, wherein the dispenser is configured to inject a molding material into the inner space of the mold chase through the injection port.
17. The apparatus of claim 16 further comprising a controller connected to the first venting port and the second venting port, wherein the controller is configured to open the first venting port and the second venting port individually at different time points.
18. The apparatus of claim 15, wherein the first size is greater than the second size, and wherein the first venting port is farther away from the injection port than the second venting port.
19. The apparatus of claim 15, wherein the mold chase has a circular shape, with the first venting port and the injection port located on opposite sides of a diameter of the mold chase, and wherein the first venting port has a greatest size among all venting ports of the mold chase.
20. The apparatus of claim 15 further comprising a plurality of venting ports at the edge ring, wherein the plurality of venting ports become increasingly smaller in size with a reduction of respective distances from the plurality of venting ports to the injection port.
Type: Application
Filed: Jun 12, 2014
Publication Date: Oct 2, 2014
Patent Grant number: 9802349
Inventors: Bor-Ping Jang (Chu-Bei), Yeong-Jyh Lin (Caotun Township), Chien Ling Hwang (Hsin-Chu), Chung-Shi Liu (Hsin-Chu), Meng-Tse Chen (Changzhi Township), Ming-Da Cheng (Jhubei City), Chen-Hua Yu (Hsin-Chu)
Application Number: 14/302,728
International Classification: B29C 45/34 (20060101);